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Introduction
The energy resources for any activity are derived from aerobic and anaerobic metabolism. At the beginning of any exercise anaerobic metabolism predominates the aerobic metabolism. During that period, which the level of oxygen consumption is below that necessary to supply all the energy demands (ATP) is known as oxygen deficit. During recovery phase additional oxygen is consumed. That oxygen consumption is known as recovery oxygen or EPOC (excess post-exercise oxygen consumption), but the most common term in use is oxygen debt. Recovery phase after exercise is always aerobically. Oxygen consumption after exercise restores the energy demands that used during exercise. During the first 3min of recovery oxygen debt restores 98.5% of the ATP and CP that used during exercise (alactacid component). After the end of the first 3min of recovery, and for the rest 15-20min oxygen dept is used primarily for the removal of lactic acid (lactacid component).
Method
As per schedule, appendix A
TABLE
#At this point of the report you must add a table with the obtained results (VESTPD Lmin-1 VC02 Lmin-1 VO2 Lmin-1 VO2 (ml.kg.min-1), against time. I couldn't add the results that i obtained.#
Analysis
1) Average of VO2 (L/min-1) recorded from the subject for the rest period:
VO2 during 2min = 0.46 L
0.46/2 = 0.23 L/min
2) Multiplied the value from step 1 by the factor of 1.10 in order to determine the position of the baseline for use in the subsequent calculation of oxygen dept:
VO2 = 0.23 L/min x 1.10 = 0.25 L/min
3) Oxygen consumption during work task:
11.77 L
4) Measure the VO2 values from the recovery period and identify the point at which it returns to baseline as calculated in step (2).
According to the graph 1(page 6), oxygen consumption (during recovery period) does not reach the point of resting value that measured in step 2. Subject during recovery period does not reach rest value for VO2. An expansion of the VO2 line will help to determine the oxygen debt (red line on the graph1 page 6). So, oxygen debt = 6.34 L
5) Add the oxygen debt (step 4) to the oxygen consumed during the exercise (step 3) to obtain the total oxygen requirement of the subject with respect to the treadmill run.
6.34 L+ 11.77 L = 18.11 L.
Data sheet
Gender: male
Weight: 85 kg
Mean VO2 during 2 minutes of rest: 0.23 L/min -1
Baseline VO2 to be used in calculation of O2 debt (VO2 x 1.10): 0.25 L/min
Total O2 consumption during exercise: 11.77 L
Total O2 debt: 6.34 L
Total O2 requirement of exercise: 18.13 L
Net O2 requirement relative to body mass: 206.9ml/kg
Estimate the magnitude of the alactacid oxygen debt: 43.6% (appendix B, p 8)
Estimate the magnitude of the lactacid oxygen debt: 56.4% --II--
Discussion
To start with, it will be valuable to divide the experiment into three stages. The first stage, is the beginning of the experiment, the subject stays relaxed. Measurement is been taken for the expired gas during resting period. The second stage is the exercise period. At this stage of the experiment subject performs exercise (running at a speed of 16 km/hr-1). Again expired air is measured during that stage. Recovery period is the last stage of the experiment. Subject again seats relaxed and the expired air is measured again. The measures of expired air are continuously between the three phases.
At the fist stage of the experiment, oxygen consumption is measured at 0.23 L/min (table 1, rest for 1 min, page 1) That is a reasonable result since subject sustains stable value on VO2 to the normal physiological value, which fluctuated at 0.25 L/min. During rest period aerobic metabolism is responsible for all the physiological processes. Cells demand for oxygen is low and cardio-respiratory system through cardiovascular system can easily supply the oxygen that cells require to generating energy (ATP). O2 consumption during rest condition remains unchanged. The only increase in VO2 can be marked during non-rest condition (exercise).
During the second stage of the experiment subject performs exercise. The exercise task includes 4 min treadmill running at a speed of 16 Km/hr-1 (table 1, yellow area). From the start of the exercise there is an expansion of VO2 (fig 1 p 6). During that period and until the end of the exercise, oxygen consumption reaches 3.43 L/min. The change of VE and therefore of VO2 is forced by the respiratory control system. Central chemoreseptors: found in the medulla, which are sensitive to H+ ions and CO2 levels, and peripheral chemoreseptors: found in carotid and aortic bodies, which are sensitive to H+ ions, CO2 and O2 levels send signals to the central controller (respiratory center in brain). Next, respiratory center (brain stem) send signals to the effectors (respiratory muscles), which are responsible for the control of ventilation. Chemical control of ventilation depends on the chemical state of blood with particular reference to blood CO2 concentration and lesser to blood O2 concentration. (Figures 2,3 page 7). During exercise CO2 elevation occurs. CO2 elevation triggers the respiratory control system and therefore an increase in ventilation occurs (figures 2,3 page 7 -during exercise period-). At the start of any exercise anaerobic metabolism predominate the aerobic metabolism. That takes place until a steady is reached (During steady state O2 consumption remains constant and all the metabolic processes performed under aerobic metabolism). For the duration of the fist 2-7 sec of the exercise ATP (approximately 5 mmol) and CP (approximately 15 mmol) stored within each kilogram of muscle are the major sources of energy (Mcardle et al 1994). Under the lack of CP anaerobic glycolysis occurs. Finally the last stage for energy supply is the aerobic metabolism (glycolysis, TCAC, electron transport system). The predomination of anaerobic metabolism takes place during the first minute (1-2) of exercise. During that period lactic acid produced. As the VE comes near to a steady state condition, the energy provided from anaerobic metabolism starts to diminish. Additionally the energy provided from aerobic metabolism starts to predominate. When the subject reaches steady state of VO2 all the energy provided through aerobic metabolism. The time taken for the subject to reach a steady state of VO2 depends on the level of fitness. The phase in which the energy that required is not provided aerobically (during the start of the exercise) is known as oxygen deficit. If the subject is trained the total oxygen consumption is greater and therefore the anaerobic components of energy transfer is proportionally smaller and as a sequence oxygen deficit is smaller. According to the graph 1(page 6) steady state of VO2 during the exercise period does not occur, therefore it can be supported that the physical condition of the subject is very poor.
The final stage of the experiment is the recovery period. Recovery can refer to the rest period taken after the end of any exercise. There are two types of recovery. The first type is the passive recovery, which takes the form of complete rest. Passive recovery occurs on the specific experiment. The second type of recovery is the active recovery. During active recovery a low-intensity exercise comes after the hard intensity exercise. According to the experiment procedure the subject after the end of the exercise sits down -on a chair- (passive recovery) for a period of 20min. during the first two minutes of recovery, oxygen consumption declines very rapidly, then more slowly until a constant rate close to resting level, is reached (figure 1 page 6 -recovery period-). According on the graph1 at page 6, there is a slight elevation of O2 consumption after the 4th min of recovery. That is not physiological since subject is rest and O2 consumption must decline until it reaches the rest values. At that point an experimental error may occur (e.g. air escape during the closure of the valves, or inaccurate combination between time and closure of valves). Again respiratory control system is responsible for the control of ventilation during recovery. There is relationship between VCO2 and VEstpd. Degrease in VCO2 is followed by decrease in VEstpd (fig 2,3 p 7-recovery period-). The additional oxygen that must be taken into the body after the end of any exercise is known as oxygen dept. The role of the oxygen dept is to restore all systems to their normal states.
Oxygen debt can be divided into two categories: a) alactacid debt (or fast component). Fast component is identified as alactacid debt because oxygen consumption during that phase is not related with the removal of lactate. b) Lactacid debt (or slow component). On the other hand, slow component is determined as lactacid debt because there is a direct relationship between oxygen consumption and lactic acid (C3H5O3- and H+) removal. Alactacid debt is the first physiological process that takes place after the end of exercise. During the first minute of the recovery breathing still remain elevated (table1 page 1). Thus, the heart remains to work hard and additional oxygen is required. Additionally respiratory muscles require more oxygen for the work of breathing. At the end of the first minute of recovery VO2 starts to decline rapidly. The first physiological process that takes place during alactacid debt phase is the resaturation of myoglobin with oxygen. In muscles the O2 myoglobin stores are small. About 11.2 ml of oxygen are stored in myoglobin per Kg of muscle mass (Merie L. Foss et al 1998). O2 myoglobin is the first source found in the muscles, which related to the production of energy. That stored O2 is used from the organism at the start of the exercise and is the first, which restored during recovery period. Alactacid dept is also responsible for the phosphagens (ATP and PC) restoration. Restoration of ATP and CP take place during the first 30 sec of recovery. That is important for the athletes that want to work on the specific source of energy.
By the time that oxygen consumption starts to decline slowly, alactacid debt phase gives his place to the lactacid debt phase. Lactacid debt occurs until the oxygen consumption reaches the rest value. According to the graph1 on page 6, subject during recovery period does not reach rest VO2 value. It can be supported that the exercise that the subject performed was hard; therefore more time was needed for the subject to reach the rest VO2 values. Lactacid debt strong linked with the removal of lactic acid. Lactic acid, which removed from the blood and the muscles during recovery is metabolically converted to glycogen, CO2 and H2 O and lesser to glucose and protein. The majority of lactic acid is oxidized to CO2 and H2 O (most of the lactic acid oxidized by the muscles, within Type I rather than Type II fibers). The remaining lactic acid is converted to glycogen. That process takes place in the liver and is known as gluconeogenesis (Cori cycle). The end product (glycogen) from gluconeogenesis can be used again as an energy fuel. Furthermore, the lactate, which produced by the ft fibers through venous circulation diffused into the adjacent muscle fibers with spare aerobic capacity for oxidized (LDH-H). Lactatedehydrogenase lactate LDH-H pyruvate TCA Cycle. LDH-H is an enzyme, which is useful for the conversion of lactate to pyruvate. That process is known as lactate shuttle. The removal of lactic acid is related on the duration and the intensity of the exercise. Is also related with the fitness condition of the performer. The more vigorous the exercise is (high intensity, long duration) the more lactate production occurs, therefore greater the time for the removal of the lactic acid. In general, after the end of maximal exercise half of the lactic acid is removed during the first 25min of rest recovery. That means that about 95% of the lactate will be removed after 1 hour and 15min or rest recovery (Merie L. Foss et al 1998). The elevated oxygen consumption during slow component (lactacid debt) is also related with the oxygen cost of ventilation, and the elevation of body temperature but the major function of slow component phase is related with the removal of lactate.
At the end of recovery, organism returns to the pre-exercise condition. That means, restoration of O2 myoglobin, CP and ATP energy sources. Also lactate portion has decline to negligible amount. All the above processes occur during 20-25min after the end of the exercise. The recovery phase ends at that point, but restoration of glycogen that has been used during exercise maintained for at least 24 hours after endurance exercise (when normal or high-carbohydrate diet is consumed). As a result the real recovery time includes not only the restoration of O2 consumption to the normal resting values but also the restoration of glycogen stores.
Conclusion
During sub-maximal exercise elevation of O2 consumption occurs. At the beginning of any exercise anaerobic metabolism predominates the aerobic metabolism. The energy provided during deficit period of exercise most likely represents non-aerobic energy. During recovery, fast component phase related with the restoration of phosphagens ATP and CP, following by the slow component phase, which related with the removal of lactate. Recovery period (alactacid debit and lactacid debt) lasts 20-25min, although glycogen restoration maintained for longer period of time.
Appendix A
Method
a) Selection of the subject that is going to perform the experiment.
b) Measurement of body weigh, room temperature, room barometric pressure, and humidity.
c) Subject asked to sit down (on a chair) at rest position for 2 minutes. Collection and measurement of expired air (VO2) for 2 minutes take place.
d) Subject is then required to run on a treadmill at a speed of 16 km/hr-1 for a period of 4 minutes. Expired air is collected every 1 minute during exercise and analyzed.
e) At the end of the exercise period subject asked to sit on a chair. Gas collection and measurement of expired air and VO2 is continuous after the exercise between 1-2, 2-3, 3-4, 6-7, 8-9, 10-11, 12-13, 14-15, 19-20 minutes.
Appendix B
Estimate the magnitude of the alactacid and lactacid oxygen debt:
Alactacid oxygen debt occurs during the first 2min of recovery. During that time 2.74L of oxygen consumed. On the other hand lactacid oxygen debt occurs for the rest period of the recovery. During that period 3.60L of oxygen consumed. The total oxygen debt is 6.34L. Therefore:
At 6.39L total oxygen debt - alactacid acid debt counts 2.79
At 100L total oxygen debt - alactacid oxygen debt x?
Therefore: 6.39 x X = 100 x 2.70
So: 279 / 6.39 = 43.6% is the alactacid oxygen debt
So the remaining 56.4% of the total oxygen debt is the lactacid acid debt
REFERENCES
Stephen R. Bird, 1992. Exercise physiology for health professionals. Great Britain: St Edmundsbury Press.
Merle L. Foss, Steven J. Kateyian, 1998. Foxs physiological basis for exercise and sport. 6th edition. Singapore: McGraw-Hill companies, Inc
William D. McArdle et al, 1994. Essentials of exercise physiology. USA: Lea & Febiger.
Gerald J. Tortora, 1974. Introduction to the human body. 4th ed. USA: RD Donnelley & Sons Company.
LINK TO: European Journal of Applied Physiology LINK TO: British Journal of Sports Medicine |
